Each of Patent Documents 1-3 discloses a brake system installed in a vehicle having four wheels, i.e., a front right wheel, a front rear wheel, a rear right wheel and a rear left wheel.
In the brake system disclosed in each of Patent Documents 1 and 2, each of the front right wheel, front left wheel, rear right wheel and rear left wheel is provided with a hydraulic brake as a friction brake.
The brake system disclosed in Patent Document 1 employs a so-called “X pipe arrangement” and has a first hydraulic line including brake cylinders of the hydraulic brakes provided for the front right wheel and the rear left wheel and a second hydraulic line including brake cylinders of the hydraulic brakes provided for the front right wheel and the rear left wheel. In this brake system, in the event of failure of one of the first and second hydraulic lines, a rate of increase of hydraulic pressure in the brake cylinders included in the other of the first and second hydraulic lines is restrained thereby making it possible to restrain a yaw moment acting on the vehicle as a result of the failure of the one of the first and second hydraulic lines.
In the brake system disclosed in the Patent Document 2, when the vehicle is braked during turning of the vehicle, the hydraulic pressure in the brake cylinder of the hydraulic brake provided for each of outside ones of the wheels, which are given a higher road holding load, is increased. Where a P valve (proportioning valve) is provided for each of the hydraulic brakes for the rear right and left wheels, an outside one of the rear right and left wheels is given an increased road holding load when the vehicle is braked during turning of the vehicle, so that the hydraulic pressure in the brake cylinder provided for the outside wheel is made higher than the hydraulic pressure in the brake cylinder provided for the inside wheel. An actuator is activated in response to the pressure difference, for increasing the hydraulic pressure in the brake cylinder of the hydraulic brake provided for an outside one of the front right and left wheels (i.e., one of the front right and left wheels which is located on the same side as the above-described outside one of the rear right and left wheels). Thus, the hydraulic pressure in the brake cylinder provided for each of the front and rear outside wheels, which is given a higher road holding load, is increased whereby a braking force acting on an entirety of the vehicle can be increased.
In the vehicle provided with the brake system disclosed in the Patent Document 3, suspension cylinders are provided for the respective four wheels, i.e., front right, front left, rear right and rear left wheels, such that each of the suspension cylinders is disposed between a body of the vehicle and a corresponding one of wheel-side members holding the respective wheels. In this brake system, upon an emergency brake activation for avoiding a collision, a vertical acceleration of the vehicle is controlled by controlling the hydraulic pressure in each of the suspension cylinders, whereby the road holding load is increased. Thus, a maximum braking force can be increased.
Patent Document 4 discloses an arrangement of a vehicle having one front wheel and two rear wheels (i.e., rear right and left wheels) in which hydraulic brakes are provided for the respective wheels, and discloses also an arrangement of a vehicle having one front wheel, one rear wheel, and right and left wheels located between the front and rear wheels. When a brake pedal is depressed by a vehicle operator, the hydraulic brakes provided for the respective wheels are activated whereby rotations of the wheels are retrained.